Offsetting its falling mobile average revenue per user (ARPU), Optus reported growth across mobile customers, up to a total of 9.8 million: 3.7 million prepaid, 5 million post-paid, and 1.04 million mobile broadband customers.

While Optus did not disclose its mobile penetration rate or market share, its 4G network now reaches more than 96 percent of the Australian population.

"The number of 4G mobile customers increased by 84,000 this quarter, resulting in the total 4G customer base increasing to 5.81 million as at 30 June 2017," Optus said.

"Optus continued to invest in its mobile networks, reaching 96.4 percent of 4G population coverage with 6,187 sites upgraded to 4G, of which 5,156 have been upgraded to 700MHz spectrum."

During the quarter, Optus also announced that it will be investing AU$1.5 billion in improving its mobile coverage across Australia -- attributing this to the government's decision not to declare wholesale domestic mobile roaming -- and last month added that it will spend AU$1 billion to build 500 new mobile sites and upgrade 1,800 sites to 4G in regional areas by the end of June 2018.

"The AU$1.5 billion primarily will go towards our mobile network, and will go towards building a significant number of new greenfields sites primarily in the regional areas," CEO Allen Lew told ZDNet in May.

"There will also be within that AU$1.5 billion a densification of our metro networks in the capital cities."

Optus also invested AU$1.5 billion in capital expenditure during the 2016-17 financial year, expanding its 4G network by deploying 4.5G services, small cells, and voice over Wi-Fi.

"Our first-quarter result is built on consistent investment in our network and the creation of content and new services that resonate with customers, with the promise of more to come," Lew said on Friday.

"Our comprehensive regional and metropolitan network investment strategy is delivering positive momentum for our business. With National Geographic and our exclusive English Premier League offerings, we are looking to expand the appeal of our content suite to even larger audiences with an appetite for premium entertainment and game-changing content."

Optus' mass-market broadband ARPU rose from AU$52 to AU$54 per month thanks to the addition of its pay TV service Fetch to this category, while the entertainment partnership with Nat Geo announced last month is part of what Lew told ZDNet is the telco's next move to become a "mobile-led multimedia service provider".